1. Field of the Invention.
The present invention pertains to a method for laying out a structural member with a laser beam and the associated apparatus. In particular, the present invention employs a free-standing laser and a protractor designed to be positioned on top of the structural member such as, for example, a pipe, so that a technician can chalk a severance line on the pipe formed by the laser beam when it is in alignment with the protractor. After the pipe has been chalked according to the process of the present invention, it is cut in any conventional manner.
2. Prior Art.
Prior art devices generally consist of a marker and an associated template or protractor. These devices usually fasten onto the pipe by means of a clamp or the like. After the pipe has been marked or scribed as desired, the device is detached from the pipe and the pipe is cut as scribed. The following patents illustrate typical pipe layout devices.
U.S. Pat. No. 2,549,911 to Lee discloses an elongated table with an adjustable pipe bed mounted atop the table for supporting pipe having a small range of diameter and lengths. A protractor plate is also mounted on the table and is set to the desired angle to which the pipe is to be cut. Once the pipe is secured on the table by means of the adjustable pipe bed and the protractor is set to the desired angle, an arm member is securely fastened to one end of the pipe to be cut. The arm member is in continual abutment with the protractor so that, as the pipe is rotated, it reciprocates longitudinally enabling a marker to scribe a severance line around the entire circumference of the pipe. After the pipe is detached from the table it is cut along the severance line.
Although the Lee patent is capable of scribing a severance line on pipe having a small range of sizes, it is incapable of scribing a line on both small diameter pipe and large diameter pipe (in the order of 4 foot or more) of any length. Moreover, the Lee patent fails to mention employing the device for scribing a beveled cut in addition to an angled cut.
U.S. Pat. No. 3,238,623 to Lee discloses a pipe layout device having a base portion which is held securely to the pipe to be marked, by means of a chain which wraps around the circumference of the pipe. Mounted upon the base portion is a guide bar which is attached to a holding arm and a holder. The guide bar includes a reference means with degree marks indicating the desired angle to which the pipe is to be cut. This device is capable of marking the entire circumference of the pipe, by first marking the upper portion of the pipe, and then sliding the holding arm to the lower portion of guide bar and marking the lower portion of the pipe.
While this device is capable of marking the entire circumference of the pipe, accuracy is lost when the holding arm is moved from the upper portion of the guide bar to the lower portion of the guide bar. Furthermore, this device is unable to cut pipe having a large range of diameters because of the limiting length of the holding arm and holder. Moreover, this device requires the pipe to be lifted or elevated in order to permit the holding arm and holder to mark the entire circumference of the pipe. Additionally, the Lee patent fails to mention employing the layout device for scribing a beveled cut and an angled cut.
Thus, a need exists for developing a device capable of indicating, on any size structural member, a severance line at precisely the angle desired. In particular, there exists a need for a device which can indicate a severance line without the need of having to lift the structural member, especially in the case of large diameter pipe. Furthermore, there is a need for a device which is capable of marking the entire circumference of the structural member without the need to adjust or relocate the template or protractor. Lastly, there is a need for a device capable of scribing both a beveled severance line and a skewed severance line.